Description: netfilter: xt_TCPMSS: add more sanity tests on tcph->doff
References:
 http://patchwork.ozlabs.org/patch/746618/
 https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1739765
 https://lkml.org/lkml/2017/4/2/13
Notes:
Bugs:
upstream: released (4.11-rc7) [2638fd0f92d4397884fd991d8f4925cb3f081901]
4.9-upstream-stable: released (4.9.36) [ced7689be60ddcac4b1746212c547e8817c5ae5e]
3.16-upstream-stable: released (3.16.54) [d2e769238e6079e1e16c856cc352b0061a111f1d]
3.2-upstream-stable: released (3.2.99) [d84eeff84e9869d29f442ff652ce1352cfa63e84]
sid: released (4.11.6-1)
4.9-stretch-security: released (4.9.47-1)
3.16-jessie-security: released (3.16.56-1)
3.2-wheezy-security: released (3.2.101-1)